Thrashing: busy CPU, no progress
Thrashing is when the machine spends its time swapping pages instead of running useful work.
free -h
vmstat 1
# si/so columns (swap in/out) climbing while apps crawl
# Who is eating RSS?
ps aux --sort=-%mem | head
Scenario: Load average is high, everything feels stuck. vmstat shows constant si/so; iostat shows swap device busy. The fix is reduce the working set (fewer replicas, smaller caches, kill the leak) or add RAM — tweaking CPU nice won’t help. Pathological cousin of resource contention: the system is fully utilized on the wrong work.